I. Field of the Invention
The present invention relates to a supercharging system for both 2-stroke cycle and 4-stroke cycle internal combustion engines.
II. Description of the Related Art
A supercharger is a device for increasing the power output of internal combustion engines. A supercharger compresses air or a mixture of fuel and air and forces it into the cylinders of the engine at a pressure greater than the pressure of the atmosphere. This compression increases the amount of air and fuel that can be burned at one time in the combustion chamber. There are two main types of superchargers. In positive displacement superchargers, the air is compressed by rotating cams, rotating vanes, or a piston. This type of supercharger is used on ground based engines and is driven from the crankshaft by gears or belts. These superchargers are mechanically complex, and therefore, due to space and weight restrictions associated with performance, they are difficult to incorporate into certain vehicles. Also, a positive displacement unit absorbs a substantial portion of engine horsepower and requires a mechanical wastegate to relieve excess pressure.
The second main type of supercharger is commonly referred to as the turbocharger. The turbocharger is used mainly on diesel engines and on airplane piston engines because it is light and compact. The turbocharger is also used with high performance automobiles, select motorcycles and certain race vehicles. With the turbocharger, the exhaust gases drive a compressor wheel to create the supercharging effect. This exhaust driven system (non-positive displacement or free floater) must generate sufficient exhaust pressures to generate a smooth and even flow of exhaust gases. To accomplish a smooth and even flow of exhaust gases, the turbo compressor generally starts pressure generation at approximately forty thousand (40,000) rpm and operates up to one hundred fifty thousand (150,000) rpm. The time necessary to accelerate to these speeds represents a lag factor. This lag factor usually affects the acceleration by compressing air late in the rpm cycle, and therefore, the turbocharger does not significantly increase performance at lower rpm's. This problem is most prevalent in small combustion engines because exhaust pulses are not frequent or smooth enough to generate the necessary compressor speeds.
A third supercharging method uses frontal air velocity to generate positive intake pressure. This system is completely dependent on forward vehicle velocity to generate intake pressure. At zero velocity (assuming no wind), no pressure is generated. As forward velocity increases, the pressure also increases at a proportional rate. At low velocities, the amount of pressure generated is too small to be of any practical use. Also, at high altitudes where the density of air decreases, the air pressure generated by forward velocity diminishes at a greater rate than the air pressure generated using mechanically driven compressors.
In order to derive substantial benefits from supercharging, the pressures between the carburetor float bowl and the primary plenum chamber of a supercharger should be balanced. A system that does not balance these pressures such as U.S. Pat. No. 4,907,552 issued to Martin can only work at pressures up to about a quarter of an inch of water. At pressures above a quarter of an inch of water, balancing these pressures becomes an absolute requirement. In an unbalanced condition, air flow, under pressure from the plenum chamber, creates a differential air pressure from the carburetor venturi to the fuel float bowl and fuel ceases to flow through the carburetor.
The multistage supercharger of the present invention produces better results for smaller engines (especially two-stroke cycle) than the prior art superchargers by combining a forward air pressure intake, a mechanical centrifugal compressor (non-positive displacement), and an electronically controlled axial flow compressor to yield a complete pressure spectrum across the entire rpm band, and by balancing the pressures between the carburetor fuel float bowl and the primary plenum chamber.